1. Field of the Invention
The present invention relates to a car audio system with a built-in hands-free, more specifically, an automatic mode converging method between an audio mode and a hands-free mode for a car audio system of which car audio kit is organically interconnected with a hands-free.
2. Description of the Related Art
It is a well-known fact that as diverse electronic communication techniques are developed, a mobile phone is something almost every one now possessed. Particularly, a car with a hands-free function is now being developed for car drivers who wish to communicate with business or personal acquaintances conveniently and safely while driving a car. In the past, this hands-free function was an option, unlike a car audio function that is one of basic parts of the car.
FIG. 1 is an electric block diagram of a related art hands-free for use with a car. As shown in FIG. 1, the hands-free for a car according to the related art is built in a separate kit 10 different from a car audio kit 20. This separate kit 10 includes a power circuit 19 for providing voltage provided from a car battery 30 to each part of the device after converting the voltage to a designated voltage, a mobile phone jack 11 for connecting an ear phone of the mobile phone 50 to the mobile phone through a wire, a microphone circuit 15 for processing an output voice signal being input through a microphone 60 that is attached to a suitable position of a car, e.g. around the ceiling above a driver, a transmission circuit 14 for transmitting the output voice signal to the mobile phone 50 through the mobile phone jack 11, a DSP (Digital Signal Processor) 13 for sending the output voice signal transmitted from the microphone circuit to the transmission circuit 14 and for processing a received voice signal provided through the mobile phone jack 11, an audio amplifier (Amp) 16 for amplifying a processed voice signal by the DSP 13, relays 17 and 18 for selectively connecting speakers 40 on both sides (right and left) in front of the car to the audio amp 16 or an electric IC (not shown) of the car audio kit 20, and a micom (hereinafter, it is referred to as a ‘hands-free micom’) 12 for controlling operations of the relays based on a decision whether the driver made a call using the mobile phone 50.
With the above constitution, if a current user is not on the phone at the moment, the hands-free micom 12 controls the relays 17 and 18, to connect a power IC of the car audio kit 20 to a front speaker 40, allowing the user to listen to music or broadcast he or she wants through the front speaker 40 and a rear speaker (not shown). On the other hand, if the user makes a call in this state, the hands-free micom 12 controls the relays 17 and 18, to connect the front speaker 40 to the audio amp 16 inside the audio kit 10, whereby a voice signal from the other end of the call is output through the front speaker 40.
However, the traditional hands-free for a car as discussed before has problems in that it occupies a lot of space primarily because the device is built in a separate kit from the car audio kit, and shares only the front speaker of the car with the car audio system. Moreover, it requires a separate voice signal processing circuit like the audio amp, and a separate power circuit. In addition, since the traditional hands-free is operated independent of the car audio system, if there is a call while music or broadcast is played from the rear speaker, it is hard for the user to catch a telephone call being output from the front speaker. Besides, speech quality is often deteriorated because a low-grade audio amp amplifies voice signals.
Moves have been under way to relieve problems with the above related art techniques, including Korean Patent Publication Nos. 2002-4153 (Publication date: Jan. 16, 2002), 2000-41692 (Publication date: Jul. 15, 2000), 2000-36639 (Publication date: July 5), 2000-26077 (Publication date: May 6, 2000), and 2000-1206 (Publication date: Jan. 15 2000. According to the teachings of the above related arts, an audio mode (this is a state where audio sounds are output through a speaker) is not automatically changed to a hands-free mode (this is a state where a telephone conversation, not the audio sounds is output through the speaker) until the driver (or the user) operates number keys on the mobile phone to input a telephone number, followed by pressing a ‘send’ key on his mobile phone. A further problem is that after the driver completes the call, he has to operate all conversion keys to switch the hands-free mode back to the audio mode.